The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Spark-ignition direct-injection (SIDI) engines include one or more fuel injectors that inject fuel directly into associated engine cylinders. While the engine is running, a fuel pump supplies fuel to a fuel rail at high pressure, e.g. 3-15 megapascals (435-2176 pounds per square inch). The fuel pump can be mechanically driven by the engine. The fuel rail provides the pressurized fuel to the fuel injectors, which inject the fuel into the cylinders at times and pulse widths that are determined by an engine control module.
When the engine is being started it takes some time for the fuel pump to raise the pressure in the fuel rail. During that time the fuel pressure may be too low for the fuel injectors to provide enough fuel to start the engine quickly and reliably. A fuel flow rate through a fuel injector is based on a pressure difference across a fuel injector nozzle. When the engine is first being started, the engine is rotating slowly and the mechanically driven fuel pump may not develop fuel pressure that exceeds pressure in the cylinders. The fuel pressure therefore may not be able to overcome the cylinder pressures as is needed to deliver fuel to the cylinder via the fuel injectors.